Neuronal protection by cerium oxide nanoparticles

ABSTRACT

A method of treating a subject with elevated levels of peroxynitrite includes administering a therapeutically effective amount of cerium oxide nanoparticles to the subject, wherein the cerium oxide nanoparticles reduce the level of peroxynitrite in the subject.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. Provisional Application No. 61/537,368 filed Sep. 21, 2011 to which priority is claimed under 35 USC 119, and is incorporated herein by reference.

FEDERAL FUNDING

This invention was made with government support under Grant Numbers R01NS047456, R01 EY016164, R01 NS055193 (to EBW) awarded by the National Institute of Health (NIH). It was also made with government support awarded by the National Institute of Health, NCRR Grant P21 RR04050, ES010337, DK 54441 (to MHE), NIH R01AG031529-01 (to WTS and SS), as well as NSF NIRT CBET 0708172 (to SS and WTS). The government has certain rights in the invention.

BACKGROUND

Neurodegeneration generally refers to the loss of structure or function of neurons, impairment of normal neuronal functions, and includes the death of neurons. Neurodegeneration results from various different causes including genetic mutation, mitochondrial dysfunction, and the inability to handle increasing levels of oxidative or nitrosative stress can also lead to the progression of neurodegeneration (67). Substantial evidence from many in vitro and in vivo studies suggests that there is a commonality of events for the progression of many neurodegenerative diseases of aging. Some of these neurodegenerative diseases include Parkinson's disease, Huntington's disease, Amyotrophic Lateral Sclerosis (ALS), and among the most common of the neurodegenerative disorders is Alzheimer's disease (AD). AD is a progressive and irreversible burden on patients, caregivers, and society (68). Mounting evidence in AD as well as in most neurodegenerative diseases shows an association with oxidative and nitrosative stress. Nitrosative stress and cell damage results when reactive nitrogen species (RNS) act together with reactive oxygen species (ROS).

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are formed during normal metabolism but an imbalance may result from the increase production of free radicals or from the failure of antioxidants and antioxidant enzymes to adequately scavenge the damaging molecules. This imbalance has been documented to be involved in AD (69). Several studies provide clear evidence that RNS, in particular peroxynitrite (ONOO⁻) formation, contributes to the pathologies of chronic neurodegenerative diseases such as AD, Parkinson's disease, multiple sclerosis, and Amyotrophic lateral sclerosis (4). Peroxynitrite is formed from the reaction of nitric oxide radical (NO·) with superoxide (O2^(·−)). Mitochondrial injury seems to be a primary cause of ONOO⁻ promoting neurotoxic effects (5, 6). Widespread ONOO⁻ mediated damage is seen in brain tissue from AD in the form of increased protein nitration in neurons (7).

The administration of antioxidants and antioxidant enzymes to treat diseases due to increased ROS and RNS in human clinical trials have heretofore been less than satisfactory due to issues with bioavailability and stability after administration.

To answer this need, synthetic catalytic scavengers of ROS and RNS have been made and tested in various model systems. Copious metalloporphyrins have been synthesized to have high reactivity with, O₂ ^(·−), H₂O₂, NO· and ONOO⁻ (14-17). Most studies affirm metalloporphyrins are useful tools for research and understanding the roles that ROS and RNS may play in diseases, however, their potential toxicity due to metals has often come into question for their use in humans.

Neurons have a high energy demand and contain several hundred mitochondria per cell and therefore have increased exposure to ROS and RNS. Mitochondria are a primary site of the intercellular formation of ONOO⁻ (12) and mitochondrial dysfunction has been shown to contribute to disease or neuronal death (13). The ability to scavenge ONOO⁻ is a critical therapeutic intercession in degenerative diseases associated the overproduction or unbalanced production of O₂ ^(·−) and NO· and thus, ONOO⁻.

To maintain their energy producing function, mitochondria must frequently divide and fuse. Evidence suggests that an imbalance in mitochondrial division and fusion plays a causal role in AD (78). Mitochondrial division and fusion is regulated by large GTPases of the dynamin family. Dynamin-related protein 1 (DRP1) is required for mitochondrial division. Inhibition of mitochondrial division by expression of the GTPase defective DRP1^(K38A) mutant provides protection against excessive NO, NMDA, or Aβ (5). The exact mechanism that accounts for the NO-induced mitochondrial fragmentation remains unclear. A recent report suggested that S-nitrosylation of DRP1 at cysteine 644 increases DRP1 activity and is the cause for the peroxynitrite-induced mitochondrial fragmentation in AD (85, 50). However, the work remains controversial, suggesting alternative pathways might be implicated (85, 86). Nitrosative stress causes rapid DRP1 Serine 616 (S616) phosphorylation, which promotes its translocation to mitochondria and organelle division (86, 87). In mitotic cells DRP1 5616 phosphorylation is mediated by Cdk1/cyclinB1 and synchronizes mitochondrial division with cell division (88, 89). Interestingly, p-DRP1 S616 levels are markedly increased in brains of individuals with AD, suggesting that this event might contribute to the change in mitochondrial morphology and energy metabolism in AD (86, 88). The kinase responsible for DRP1 5616 hyperphosphorylation in AD is unknown, but Cdk5/p25 is a potential candidate kinase mediating this process (7, 90). Notably, aberrant Cdk5/p25 signaling causes tau hyperphosphorylation in postmitotic neurons and is implicated in Aβ-mediated neurodegeneration (88, 91-93).

SUMMARY

The effects that Alzheimer disease and other neurodegenerative diseases have on the brain include physical changes in the brain. Some of those changes include the development of characteristic plaques and neurofibrillary tangles. The activation of microglia in response to injury, illness, aging or other causes initiates events that are characterized as an inflammatory process. These events are first mediated by the proinflammatory cytokine interleukin 1, which is overexpressed by the activated microglia. Through various pathways, interleukin 1 causes neuronal death, which activates more microglia, which in turn releases more interleukin 1 in a self-sustaining and self-amplifying fashion. Over time, this slow, smoldering inflammation in the brain destroys sufficient neurons to cause the clinical signs of Alzheimer disease.

Cerium oxide nanoparticles (CeO₂ NPs) have recently been shown to effectively scavenge reactive oxygen species in a variety of model systems. The mechanism by which cerium oxide nanoparticles catalyze these redox reactions relate to the surface chemistry and redox state of cerium and is preparation dependent. Peroxynitrite, a highly neurotoxic reactive nitrogen species is functionally implicated in the pathogenesis of a broad spectrum of neurodegenerative disorders. Scavenging peroxynitrite provides beneficial therapeutic effects in both neurodegenerative diseases and in many diseases where inflammation in the brain is a critical contributing factor. Conventional antioxidants primarily scavenge only reactive oxygen species, and are ineffective against reactive nitrogen species. It has been discovered that cerium oxide, a rare earth oxide nanomaterial, scavenges peroxynitrite in vitro. This newly discovered catalytic property of cerium oxide provides protection in a primary neuronal cell model. Cerium oxide nanoparticles are internalized by neurons and accumulate around mitochondria, the primary source of reactive nitrogen species in neurons. Cerium oxide nanoparticles convey neuroprotection against exogenous nitric oxide or endogenous peroxynitrite mediated by mitochondrial toxins, excess glutamate or Meta peptide. Neuroprotection by these rare earth nanoparticles is accompanied by lower protein tyrosine nitration and reduction of reactive nitrogen species. Given the critical role that peroxynitrite plays in neurodegenerative diseases, a novel discovery that cerium oxide nanoparticles present a new therapeutic approach to lowering peroxynitrite levels and preventing neurodegeneration has been made.

Cerium oxide nanoparticles have low toxicity (18, 19). It has been discovered that the ability to switch between the 3⁺ and 4⁺ oxidation states gives CeO₂ NPs a unique antioxidant function.

CeO₂ NPs have been shown to protect several cell types and animal models against ROS mediated diseases (20). Nanoparticles in general exhibit novel surface properties that can affect their chemistry and their interaction with biological systems. CeO₂ NPs are comprised of a crystalline lattice and due to their nanometer length scale, oxygen defects at the surface are present that yield reactive sites. Within these sites, CeO₂ NPs have the ability to interchange between the 3⁺ and 4⁺ oxidation state (21). The relative level of vacancies and thus reactive sites is difficult to control, however success has been achieved herein in generating CeO₂ NPs with varied ratios of Ce in the 3⁺/4⁺ state. CeO₂ NPs with higher 3⁺/4+ ratio are superoxide dismutase (SOD) mimetics and exhibit efficient SOD activity (21, 22) when compared to CeO₂ NPs with lower 3⁺/4⁺ ratio. It should be noted that CeO₂ NPs with lower 3⁺/4⁺ ratio exhibit increased catalase mimetic activity (23). Indeed, CeO₂ NPs have been shown to be neuroprotective in various neuronal culture models (24-26). Recent in vivo studies affirm the antioxidant effects of CeO₂ NPs with low toxicity to the brain in rodent models (27, 28). The ability of CeO₂ NPs to react with ONOO⁻ in vitro and an assessment of the neuroprotective properties of CeO₂ NPs during nitrosative stress is provided herein. Also provided herein is a demonstration that certain CeO₂ NPs protect against Aβ-induced DRP1 5616 hyperphosphorylation, mitochondrial fragmentation and neuronal cell death

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a transmission electron microscopy (TEM) showing a control culture.

FIG. 1B-C is a TEM showing CeO₂ NPs within the neurons, associated with mitochondria and plasma membranes.

FIG. 1D is a chart showing the quantification of CeO₂ NPs associated with mitochondria.

FIG. 1E is a chart showing the quantification of CeO₂ NPs associated with plasma membrane.

Supplementary FIGS. 1A-D provides the physico-chemical properties of CeO₂ NPs.

FIG. 2A and Supplementary FIG. 3A-B shows graph views of a UV visible spectroscopy used to examine the strong absorbance peroxynitrite exhibits at 302 nm and its decay. The decay of ONOO⁻ was followed in the absence and presence of CeO₂ NPs.

FIG. 2B provides a graphical representation of ONOO⁻ scavenging abilities of CeO₂ NPs, viewable by following the yield of oxidized APF by fluorescent spectroscopy using the oxidizable probe, 3′-(p-aminophenyl) fluorescein (APF) as an indicator.

Supplementary FIG. 2 shows a TEM section without post-stain providing a view of CeO₂ NPs in cortical neurons.

FIG. 3A provides a comparison of the effects on cortical neuronal cultures of CeO₂, SNOC, and CeO₂+SNOC.

FIG. 3B shows a further quantitative analysis using fluorescence, determined by total pixel per intensity per μm².

FIG. 4A shows the protective effects of pre-treatment with CeO₂ NPs on cortical neurons in the right panel, the left panel provides a control view, and the center panel provides a view showing cell death.

FIG. 4B-D shows a comparison between CeO₂ NPs and NAC (N-acetyl-L-cysteine), the effect of CeO₂ NPs on neurons challenged with glutamate, and the effect of CeO₂ NPs on cell death caused by overstimulation of NMDA receptors.

FIGS. 5A-D shows the effect of CeO₂ NPs on 3-nitrotyrosine modification in an in vitro cell culture.

FIGS. 6A-B show CeO₂ NPs increasing cell viability from Aβ treatments and attenuate Aβ oligomerization.

FIG. 7 Nanoceria prevent Aβ-induced mitochondrial fragmentation. (a) Fluorescence micrographs (scale bar, 50 μm) and 3×zoom of boxed regions of mitochondrial morphology in neurons expressing DsRed2-Mito and a(a) left untreated or treated with a(b) nanoceria (100 nM) (3 h pretreatment), a(c) or Aβ 25-35 (10 μM), a(d) nanoceria and Aβ 25-35, a(e) NAC (50 μM) (3 h pretreatment), a(f) NAC and Aβ 25-35, a(g) or the reverse Aβ 35-25 (10 μM) peptide for six hours. (b) Mitochondrial fragmentation in neurons expressing DsRed2-Mito and after treatment for six hours with nanoceria, NAC, or Aβ 25-35 alone or in combination with either nanoceria and Aβ 25-35 or NAC and Aβ 25-35. Data are representative of three or more independent experiments. Results are means±s.d. Statistics: Student's t test.

FIG. 8 Nanoceria abolish DRP1 phosphorylation at 5616 in response to RNS. (a) Western blots of p-DRP1 5616, total DRP1, and actin protein levels from neurons exposed for three hours to aged SNOC (100 μM), nanoceria (100 nM) (3 h pretreatment), or fresh SNOC (100 μM) alone or in combination. The bar graph represents the relative ratios of p-Drp1 5616 to total DRP1 protein and normalized to actin. (b) Western blots of p-DRP1 5616, total DRP1, and actin protein levels from neurons exposed to nanoceria (100 nM), preaggregated 10 μM Aβ 25-35 for 6 h, or in combination as well as NAC (50 μM) (3 h pretreatment) with Aβ 25-35. The bar graph illustrates the relative ratios of p-DRP1 5616 to total DRP1 protein, normalized to actin.

FIG. 9 Nanoceria delay neuronal cell death induced by Aβ, NMDA, glutamate, or 3-NP. (a) Cell death of neurons treated with either nanoceria (100 nM) (3 h pretreatment), NAC (50 μM) (3 h pretreatment), or Aβ 25-35 (10 μM) alone, or both nanoceria and Aβ 25-35, or NAC and Aβ 25-35 at six hours. Untreated cells or reverse Aβ 35-25 (10 μM) peptide treatment served as negative controls. (b) Excitotoxic cell death of neurons exposed to either NMDA (150 μM), or nanoceria (100 nM) (3 h pretreatment), or in combination of both for 12 hours. (c) Excitotoxic cell death of neurons exposed to either glutamate (150 μM), or nanoceria (100 nM) (3 h pretreatment), or in combination of both for six hours. (d) Cell death of neurons exposed to mitochondrial respiratory complex II inhibitor 3-NP (10 mM), or nanoceria (100 nM) (3 h pretreatment), or in combination of both for eight hours. Results are representative of three or more independent experiments. Data are means±s.d. Statistics: Student's t test.

DETAILED DESCRIPTION

The specifics of the discovery include the use of cerium oxide nanoparticles that specifically decrease peroxynitrite levels in a subject to treat specific conditions such as Alzheimer's disease and other neurodegenerative diseases as outlined below.

In one embodiment, a method of treating a subject with elevated levels of peroxynitrite, is provided, the method includes administering a therapeutically effective amount of cerium oxide nanoparticles to the subject, wherein the cerium oxide nanoparticles reduce the level of peroxynitrite in the subject. In a particular embodiment, the cerium oxide nanoparticles range between 1-5 nanometers in size. In another embodiment, the cerium oxide nanoparticles range between 5-10 nanometers in size. In another embodiment, the method is provided wherein the cerium oxide nanoparticles scavenge peroxynitrite.

In yet another embodiment, a method of treating a subject identified as at risk of developing a neurodegenerative disease is provided. The method includes administering a therapeutically effective amount of cerium oxide nanoparticles (CeO2NPs) to the subject, wherein the cerium oxide nanoparticles scavenge reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the subject. In a specific embodiment, the method is provided wherein the RNS is peroxynitrite.

In another embodiment, the cerium oxide nanoparticles used and which are effective to scavenge peroxynitrite have a higher ratio of 3+ to 4+ state. Reference to cerium oxide nanoparticles having a higher 3+/4+ ratio means that the percentage of cerium in the 3+ state is greater than the percentage of cerium in the 4+ state. In a more specific embodiment, a higher 3+/4+ ratio means that the percentage of cerium in the 3+ state is greater than 50 percent.

Neurodegenerative diseases include but are not limited to Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Friedreich's ataxia, Huntington's disease, or Lewy body disease. A subject at risk of developing a neurodegenerative disease can be identified by detecting or observing a number of different signs and symptoms in the subject. Some of those signs and symptoms include amyloid plaques in the brain, and/or neurofibrillary tangles (NFTs) in the brain.

In the case of Alzheimer's disease, eight cognitive domains are most commonly impaired, including memory, language, perceptual skills, attention, constructive abilities, orientation, problem solving and functional abilities (70).

Also, a decrease in activity in the temporal lobe is observed in AD development, such as through the use of known imaging techniques such as PET scan or MRI. Thus, according to one embodiment, a patient at risk would be an individual who has impairment in cognition and/or decreased activity in the temporal lobe. When available as a diagnostic tool, single photon emission computed tomography (SPECT) and positron emission tomography (PET) neuroimaging are used to confirm a diagnosis of Alzheimer's in conjunction with evaluations involving mental status examination (71). In a person already having dementia, SPECT appears to be superior in differentiating Alzheimer's disease from other possible causes, compared with the usual attempts employing mental testing and medical history analysis (72).

A new technique known as PiB PET has been developed for directly and clearly imaging beta-amyloid deposits in vivo using a tracer that binds selectively to the A-beta deposits. The PiB-PET compound uses carbon-11 PET scanning. Recent studies suggest that PiB-PET is 86% accurate in predicting which people with mild cognitive impairment will develop Alzheimer's disease within two years, and 92% accurate in ruling out the likelihood of developing Alzheimer's. A similar PET scanning radiopharmaceutical compound called (E)-4-(2-(6-(2-(2-(2-([¹⁸F] -fluoroethoxy)ethoxy)ethoxy)pyridin-3-yl)vinyl)-N-methyl benzenamine, or ¹⁸F AV-45, or florbetapir-fluorine-18, or simply florbetapir, contains the longer-lasting radionuclide fluorine-18, has recently been created, and tested as a possible diagnostic tool in Alzheimer's patients. Florbetapir, like PiB, binds to beta-amyloid, but due to its use of fluorine-18 has a half-life of 110 minutes, in contrast to PiB's radioactive half life of 20 minutes. Wong et al. found that the longer life allowed the tracer to accumulate significantly more in the brains of the AD patients, particularly in the regions known to be associated with beta-amyloid deposits. Thus, in specific embodiment, a patient at risk is one that has increased a-beta deposits.

Volumetric MRI can detect changes in the size of brain regions. Measuring those regions that atrophy during the progress of Alzheimer's disease is showing promise as a diagnostic indicator. Thus, according to another specific embodiment, an at-risk patient is one that has an atrophic brain region.

Another recent objective marker of the disease is the analysis of cerebrospinal fluid for amyloid beta or tau proteins, both total tau protein and phosphorylated tau_(181P) protein concentrations. Searching for these proteins using a spinal tap can predict the onset of Alzheimer's with a sensitivity of between 94% and 100%. Thus, according to another specific embodiment, a patient at risk is one that has elevated levels of tau and/or amyloid beta proteins in cerebral spinal fluid. When used in conjunction with existing neuroimaging, doctors can identify patients with significant memory loss who are already developing the disease (73). Spinal fluid tests are commercially available, unlike the latest neuroimaging technology. Alzheimer's was diagnosed in one-third of the people who did not have any symptoms in a 2010 study, meaning that disease progression occurs well before symptoms occur. Changes in brain ventricle size may be measured by magnetic resonance imaging (MRI). This measurement provides, in another embodiment, the ability to diagnose pre-Alzheimer' s disease or early stages of the disease in some cases. While neuro-cognitive assessments including the testing of memory, ability to problem solve, count, and other cognitive tests provides a diagnosis for Alzheimer's disease, a definitive diagnosis is not possible in the prior art until after death when an autopsy can be used to reveal the presence of amyloid plaques and tangles in brain tissue. Improvements have been made such that an earlier diagnosis may be made by identifying an increase in ventricle size in the brain associated with mild cognitive impairment in patients at risk for Alzheimer's disease or in the early stages of the disease. Therefore, according to a specific embodiment, a patient is at risk for a neurodegenerative disease, particularly AD, if the patient exhibits one or more of the foregoing factors or symptoms. In another specific embodiment, a patient at risk exhibits two or more of the aforementioned factors or symptoms.

In the case of Parkinson's disease (PD), a pattern of reduced dopaminergic activity in the basal ganglia can aid in diagnosis. Thus, in another specific embodiment, a patient at risk is one that has reduced dopaminergic activity in the basal ganglia. Also, Parkinson's disease affects movement, producing motor symptoms, such as Parkinsonian gait, tremors, rigidity, slowness of movement and postural instability. Non-motor symptoms, which include autonomic dysfunction, neuropsychiatric problems (mood, cognition, behavior or thought alterations), and sensory and sleep difficulties, are also common. Thus, according to another specific embodiment, a patient at risk is one that exhibits one or more motor or non-motor PD symptoms. In an even more specific embodiment, a patient at risk is one that has two or more of the foregoing factors or symptoms.

In a further embodiment, a method of reducing brain inflammation in a patient is provided. The method includes administering a therapeutically effective amount of cerium oxide nanoparticles to the patient, the cerium oxide nanoparticles effective to reduce peroxynitrite levels in the brain.

In still a further embodiment, a method of scavenging reactive nitrogen species in a subject is provided. The method includes administering a therapeutically effective amount of cerium oxide nanoparticles to the subject, wherein the cerium oxide nanoparticles associate with a membrane in the subject and accelerate decomposition of the reactive nitrogen species in the subject. The method is provided wherein the reactive nitrogen species is peroxynitrite. In a more specific embodiment, the membrane is a mitochondrial membrane and/or a plasma membrane.

The following examples are provided as an aid in examining particular aspects of the invention, and represent only certain embodiments and explanations of embodiments. The examples are in no way meant to be limiting of the invention scope. The materials and methods provided below are those which were used in performing the examples that follow.

EXAMPLES Example 1 Cerium Oxide Nanoparticles are Taken Up and Localize to the Periphery of Mitochondria and the Inner Surface of the Plasma Membrane in Primary Cortical Neurons

Uptake of nanomaterials by cells has been shown to vary depending upon nanoparticle size, shape, composition, as well as surface modifications. In addition, diverse cell types control differentially the uptake and translocation of nanoparticles (33). Understanding cellular responses to nanoparticles are vital to their becoming therapeutic, therefore the way in which cells internalize and traffic the CeO₂ NPs was a critical discovery.

Pure cortical neuronal cultures were treated with 100 nM CeO₂ NPs for 3, 12 and 24 h and processed for transmission electron microscopy (TEM). Compared to control cultures (FIG. 1A), CeO₂ NPs were found within the neurons, however, CeO₂ NPs were not found in the nuclei of the neurons (FIG. 1B). CeO₂ NPs were identified in two primary locations, one associated with mitochondria and a second along the plasma membranes (FIG. 1B&C). Quantification of CeO₂ NPs association with mitochondria (FIG. 1D) or plasma membrane (FIG. 1E) show their location aligns with the primary sources of reactive nitrogen species in neurons. The physico-chemical properties of CeO₂ NPs were determined using parallel samples to confirm the 3 ⁺ oxidation state, fluorite structure and cerium spectrum (Supplementary FIG. 1A-D Physico-Chemical Properties of Cerium Oxide Nanoparticles (CeO2 NPs). A. Table listing the properties of the CeO2 NPs used in this study are typical and indicative of CeO2 NPs in the 3+ state. B. Energy-dispersive X-ray (EDX) analysis of CeO2 NPs supports presence of both cerium and oxygen. C. Selected area (electron) diffraction (SAED) pattern of CeO2 NPs corresponds to fluorite pattern for ceria. D. UV-Vis graph of sterile filtered CeO2 NPs used in tissue culture experiments confirming 3+ oxidation state of CeO2 NPs. Absorbance between 230-260 nm is indicative of Ce 3+ oxidation state.). The size of the CeO₂ NPs averaged between 3-8 nm with zeta potentials measuring 5.62 eV for nanoparticles added to the neuronal cultures and zeta potentials measuring −16.26 mV in phosphate buffer in the in vitro assays, as previously reported (34). It is characteristic for oxide nanoparticles to rapidly agglomerate in biological fluids (35) due to a correlation between surface charge and opsonization (36) along with their sensitivity to local environments. To confirm that the electron dense granules seen in cells originated from the CeO₂ NPs treatment, non-post-stained images (Supplementary FIG. 2 CeO2 NPs in cortical neurons. TEM section without post-stain assures that the dense particles are from addition of CeO2 NPs and not due to staining artifact) showed the same agglomerated, 15-25 nm dense particles as the post-stained images. High resolution (HR)-TEM of the water-based CeO₂ NPs used in the TEM experiments show the characteristic (111) ceria surface (FIG. 1B inset). CeO₂ NPs were identified in cortical cultures, especially located in close proximity to membranes.

Example 2 Effect of CeO₂ NPs on the Rate of Decay of ONOO⁻ In Vitro

Peroxynitrite's involvement in many diseases makes it a concern that must be addressed (4). The half-life of ONOO− is on the order of seconds at physiological pH but that is enough time for it to diffuse a long distance to a target site. To initiate the potential use of CeO₂ NPs for therapeutic use, the effect that CeO2 NP had on the decomposition of ONOO− was tested.

Peroxynitrite exhibits a strong absorbance at 302 nm and its decay can thus be followed using UV-visible spectroscopy (37). The decay of ONOO⁻ was followed in the absence and presence of CeO₂ NPs (FIG. 2A and Supplementary FIG. 3: Effect of CeO2 NPs on the rate of decay of ONOO− in vitro varying pH. ONOO− (25 μM) was added at various pH's alone and in the presence of CeO2 NPs (100 μM), SiO2 NPs (100 μM), glutathione (GSH) (0.5 mM). (A) Peroxynitrite absorbance followed at 302 nm in 100 mM sodium phosphate buffer at pH 8.6. (N=4). GSH, known general scavenger and SiO2 NPs were added as positive and negative controls, respectively. Rate of ONOO− (black traces) decomposition was increased with CeO2 NPs (blue traces) in a similar manner of GSH (red traces). Rate of decomposition was not affected by presence of SiO2 NPs (green traces). B) 100 mM sodium phosphate buffer at pH 9.5. (N=3). Rate of ONOO− (black traces) decomposition was increased with CeO2 NPs (blue traces) in a similar manner of GSH (red traces). Absorbance was normalized by subtracting the final absorbance from initial absorbance and dividing by the amplitude. As stock solutions of ONOO− contain 0.3 M NaOH, control incubations were performed with equivalent amounts of NaOH. All in vitro experiments were performed using phosphate buffers containing 1 μM DPTA.). The in vitro assays were repeated using various phosphate buffers while varying the pH's. Since carbon dioxide is known to enhance the rate of ONOO⁻ decomposition (38), the change in absorbance at 302 nm was followed in potassium phosphate buffer (pH 8.0), which was degassed by argon. The rate of ONOO⁻ decomposition was increased by the addition of CeO₂ NPs in a manner comparable to uric acid, a known scavenger of ONOO⁻ (FIG. 2A). Similarly, the rate of ONOO⁻ decomposition was increased in the presence of CeO₂ NPs in sodium phosphate buffer at both pH 8.6 and 9.5 (Supplementary FIG. 3A&B). This change of absorbance in response to addition of CeO₂ NPs in these studies also mimics the scavenging seen with glutathione, a known antioxidant that protects cells from free radicals and peroxides (39). To confirm specificity, an unrelated oxide NP was tested, (silicon oxide (SiO₂) NPs) to determine if this potential scavenger behavior was unique to CeO₂ NPs. SiO₂ NPs did not accelerate the decay of ONOO⁻. Addition of ONOO⁻ after two minutes again resulted in faster decomposition of ONOO⁻ in the presence of CeO₂ NPs, showing that these reactions are catalytic and the catalyst is not degraded significantly during the reaction. In every case the rate of decomposition of ONOO⁻ in the presence of CeO₂ NPs was faster reflecting a reaction between ONOO⁻ and the CeO₂ NPs.

Example 3 CeO₂ NPs Interact with ONOO⁻ In Vitro and Prevent APF Oxidation

To obtain further insight into the ONOO⁻ scavenging abilities of CeO₂ NPs, the yield of oxidized APF was followed by fluorescent spectroscopy using the oxidizable probe, 3′-(p-aminophenyl)fluorescein (APF) as an indicator (FIG. 2B). APF is an aromatic amino-fluorescein derivative that has little intrinsic fluorescence but undergoes oxidation by only hydroxyl radical, hypochlorate ion, and certain peroxidase intermediates such as ONOO⁻, but is inert to NO·, O₂ ^(·−) and H₂O₂ (40). CeO₂ NPs prevented the oxidation of APF in a manner that was similar to glutathione and uric acid, known scavengers of ONOO⁻ (41). Again, an unrelated oxide NP was tested (SiO₂ NPs) which did not scavenge ONOO⁻ and thus did not prevent the oxidation of APF. Thus evidence has been found that CeO₂ NPs can facilitate ONOO⁻ decomposition using two, independent methods to measure ONOO⁻.

Example 4 CeO₂ NPs Reduce ONOO⁻ in Cortical Neuronal Cultures

RNS, in particular ONOO⁻ formation, contributes to the pathologies of chronic neurodegeneration including AD (7). To test this hypothesis, the in situ ONOO⁻ formation in live cells was followed again using the oxidizable probe, APF as an indicator. Exogenous NO· was added to mixed cortical neuronal cultures using the NO. donor S-nitrosocysteine (SNOC). Neurons treated with SNOC causes NO·/ONOO⁻ inhibition of the respiratory chain complexes (42) leading to alterations in mitochondrial function. In FIG. 3A, the lower left panel contains a representative image of cortical neuronal cultures when challenged with SNOC. The presence of ONOO⁻ is denoted by an increase of fluorescence. When dosed with CeO₂ NPs, the fluorescence is decreased (FIG. 3A lower right panel). Further quantitative analyses using fluorescence was determined by total pixel intensity per μm² (FIG. 3B). Cells exposed to CeO₂ NPs before SNOC addition had appreciably reduced fluorescence compared to cells treated with SNOC alone reflecting a lower level of ONOO⁻.

Example 5 Cortical Neuronal Cultures are Protected from Nitrosative Stress by Pretreatment with CeO₂ NPs

It was tested whether CeO₂ NPs would rescue neurons from a variety of stressors that would increase an imbalance between RNS and endogenous antioxidants. To assess the neuronal protection capabilities of CeO₂ NPs, pure cortical neuronal cultures transfected with DsRed2-Mito were pretreated with CeO₂ NPs (100 nM) and subjected to various treatments known to increase RNS. Representative images show control neuronal cells with elongated mitochondria with normal euchromatin in the soma of the neurons (FIG. 4A left panel). Cell death was evaluated by condensed nuclei accompanied by shrunken soma and mitochondrial fragmentation (FIG. 4A center panel). Pretreatment of neurons with CeO₂ NPs rescued neurons as visualized by return of soma to normal size, nuclei were no longer condensed and mitochondria were again elongated (FIG. 4A right panel). 3-Nitropropionic acid (3-NP) is an irreversible inhibitor of complex II and is toxic to neurons via an N-methyl-D-aspartate (NMDA) and reactive oxygen species (ROS) dependent pathway (30).

CeO₂ NPs were able to prevent neuronal cell death by 3-NP. These results modeled N-acetyl-L-cysteine (NAC), a well characterized cell culture antioxidant which is rapidly metabolized to intracellular glutathione (FIG. 4B). Early stages of acute glutamate induced neurotoxicity includes elevated ONOO⁻ production (43), (44). Again, CeO₂ NPs were neuroprotective after neurons were challenged with glutamate (FIG. 4C). Additionally, death caused by overstimulation of NMDA receptors with NMDA was overcome when CeO₂ NPs were present (FIG. 4D). These results suggest that in the presence of CeO₂ NPs, reactive ONOO⁻ is removed and cortical neurons are rescued from cell death caused by nitrosative stress.

Example 6 CeO₂ NPs Reduce 3-Nitrotyrosine Modification in In Vitro Cell Culture

Neurons have a high energy demand and contain several hundred mitochondria per cell and therefore have increased exposure to reactive oxygen species (ROS) and RNS (13). Mitochondria are also a primary site of the intercellular formation of ONOO⁻ (45). To understand the mechanism of neuronal protection seen by CeO₂ NPs, ONOO⁻ and its ability to promote the nitration of tyrosine residues was considered. To substantiate that CeO₂ NPs can scavenge ONOO⁻ and prevent the post-translational modification 3-nitrotyrosine, exogenous NO· was added to mixed cortical neuronal cultures using SNOC. To assay whether this protection from cell death was due to nitration of proteins, cultures were probed using an antibody specific for the addition of a nitro (—NO₂) group on the position 3 of tyrosine residues (3-NT). As seen in representative images, an increase in of 3-NT signal in SNOC treated cortical neurons was seen (FIG. 5A center right panel) whereas treatment of neuronal cultures with CeO₂ NPs reduced the 3-NT signal (FIG. 5A far right panel). These cultures were scored for cell death and it was observed that treatment with CeO₂ NPs rescued the SNOC treated cultures from cell death (FIG. 5B). This data was corroborated when images were assessed by semi-quantitative immunofluorescence. A decrease in the 3-NT signal in cultures pretreated with CeO₂ NPs was detected (FIG. 5C). These results indicate a protective effect afforded by the CeO₂ NPs ability to scavenge ONOO⁻.

Relative nitrotyrosine immunoreactivity was analyzed in cortical neuronal whole cell lysates. Positive 3-NT labeling of SNOC treated lysates showed many potential biological targets are nitrated. However, as measured by densitometry, pretreatment with CeO₂ NPs abrogated the 3-NT formation (FIG. 5D). This demonstrates CeO₂ NPs may act by attenuating the damaging effects of ONOO⁻ by reducing 3-NT modification of brain proteins. Together, this data shows that nitration of tyrosine residues mediated by ONOO⁻ can be abolished by the antioxidant properties of CeO₂ NPs.

Example 7 CeO₂ NPs Increase Cell Viability from A⊖ Treatments and Attenuate Aβ Oligomerization

The amyloid precursor protein (APP) and its cleavage products are thought to trigger a series of events that result in neurodegeneration. The increased production of Aβ and the incorporation into oligomers with subsequent deposition into plaques has been correlated with the progression of AD (46). Aβ (25-35) peptide is found in senile plaques and degenerating hippocampal neurons in AD brains but not in age-matched control subjects (47). Aβ (25-35) is the shortest peptide sequence that retains biological activity and exhibits large β-sheet structures (48). The Aβ (25-35) peptide very rapidly aggregates (49) and was allowed to oligomerize at RT for 24 h (5) before adding to pure neuronal cultures. The Aβ (25-35) treatment led to significant reduction in cell viability which was relieved by pretreatment with CeO₂ NPs in a manner that similar to pretreatment with NAC (FIG. 6A). The reverse peptide, Aβ (35-25) had no effect on cell death. This exposure to oligomerized Aβ is dependent upon the NMDA type receptor activity (9) which leads to increased nitrosative stress through activation of nNOS (50). These results show that CeO₂ NPs treatment protects neurons against acute Aβ-induced nitrosative stress.

The plaques of AD patients consist of accumulated Aβ (1-40) and Aβ (1-42) (51) and these are widely believed to contribute to neurotoxicity and AD pathogenesis. The neurotoxicity of the Aβ peptides is due at least in part to the production of ROS through metal ion reduction (52). To test whether CeO2 NPs could impart protection against β-amyloid fibril formation, 1 μg of Aβ (1-40) peptide was allowed to oligomerize for 7 days in the presence of increasing amounts of CeO₂ NPs and oligomer formation was analyzed using a protocol modified from Kayed et al. (53). The peptides were then dot blotted onto nitrocellulose and probed with an antibody which recognizes the oligomeric and not the monomeric form. Densitometric analysis of the dot blot shows Aβ fibril formation was attenuated with addition of increasing amounts CeO₂ NPs (FIG. 6B). In contrast, SiO₂ NPs did not affect the oligomerization. These results indicate CeO₂ NPs, even in the presence of the metal chelator diethylenetriaminepentaacetic acid (DPTA), were able to inhibit the formation of β-amyloid fibrils. Therefore, the protective role of the CeO₂ NPs in protection against β-amyloid toxicity is likely to be a combination of ROS and RNS scavenging properties.

Example 8 Nanoceria Protect Against AP-Induced Mitochondrial Fragmentation

Nitrosative stress plays an important role in Aβ-mediated neurotoxicity (94, 95). Aβ or nitrosative stress evoke persistent mitochondrial fragmentation, an event that causes bioenergetic failure, impaired Ca²⁺ homeostasis, synaptic injury, axonal transport defects, and neuronal cell death (5, 96). To test whether nanoceria would prevent the Aβ-induced mitochondrial fragmentation, the mitochondrial morphology by fluorescence microscopy in neurons expressing DsRed2-Mito, a red fluorescent protein targeted to the mitochondrial matrix was visualized. Control neurons,—either left untreated or treated with nanoceria alone (3 h pretreatment)—, demonstrated an elongated mitochondrial morphology, typical of healthy neurons (FIGS. 7 a(a) and 7 a(b)). By contrast, oligomeric Aβ 25-35 peptide, but not the reverse Aβ 35-25 control peptide (FIG. 7 a(g)), induced dramatic mitochondrial fragmentation evidenced by the appearance of mitochondria with mostly round morphology (FIG. 7 a(c)). Remarkably, nanoceria prevented the Aβ 25-35-induced mitochondrial fragmentation, similar to N-acetyl-L-cysteine (NAC), a known NO/ONOO⁻ neutralizing antioxidant supplement (FIGS. 7 a(d) and 7 a(f)). Further quantitative analysis demonstrated that nanoceria significantly reduced the Aβ-induced mitochondrial fragmentation in neurons (FIG. 7 b). These results suggest that nanoceria not only accumulate at mitochondria, but can also preserve their morphology and function in response to neurotoxic insults such as Aβ.

Example 9 Nanoceria Reduce DRP1 Phosphorylation at S616

There is increasing evidence that mitochondrial fragmentation, owing to excessive DRP1-dependent mitochondrial fission, plays a central role in many neurodegenerative disorders including AD (87). Cdk1/cyclinB1-mediated phosphorylation of DRP1 at 5616 causes its recruitment from the cytoplasm to mitochondria to initiate organelle division in mitotic cells (88). However, all Cdk's are inactivated in postmitotic neurons with the exception of Cdk5. Over-activation of NMDA receptors by Aβ triggers excessive nitrosative stress and cytoplasmic Ca²⁺ levels. (20) possibly leading to increased NO production. SNOC triggers DRP1 5616 phosphorylation and mitochondrial fragmentation (5, 86). Notably, p-DRP1 5616 is increased in AD patient brains (86, 90, 97). Because nanoceria prevented Aβ-induced mitochondrial fragmentation (FIG. 7), it was questioned whether they might inhibit DRP1 5616 phosphorylation, providing an explanation for the preservation of mitochondrial morphology by nanoceria. Neurons treated with either aged SNOC or nanoceria alone exhibited only low baseline DRP1 5616 phosphorylation (FIG. 8 a). By contrast, neurons treated with fresh SNOC exhibited high p-DRP1 S616 levels (FIG. 8 a). Remarkably, nanoceria significantly reduced the SNOC-induced increase in DRP1 5616 phosphorylation (FIG. 8 a). Similarly, nanoceria or NAC abolished the Aβ 25-35-induced DRP1 5616 phosphorylation (FIG. 8 b). These results suggest that nanoceria reduce nitrosative stress or Aβ-induced mitochondrial fragmentation perhaps by preventing DRP1 5616 hyperphosphorylation.

Example 10 Nanoceria Protect Against Aβ-Induced Neuronal Cell Death

Cell death by Aβ or NMDA occurs, at least in part, through endogenous RNS/ROS (5). Neuronal death by the complex II inhibitor 3-nitropropionic acid (3-NP) triggers secondary excitotoxicity and RNS/ROS (30). Aβ 25-35, but not the reverse peptide, elicited neuronal cell death, which was reduced in the presence of either nanoceria or NAC (FIG. 9 a). Similarly, neuronal cell death by excess NMDA or glutamate was reduced by nanoceria (FIGS. 9 b and 9 c). Finally, similar neuroprotective effects were observed against respiratory complex II inhibition by 3-NP (FIG. 9 d). Thus, nanoceria provide neuroprotection against a variety of insults that generate endogenous ROS/RNS.

A mode of action for the way in which CeO₂ NPs may attenuate RNS in cells which could have far reaching implications in neurodegenerative diseases has been described herein. In the present study, CeO₂ NPs were investigated and it was found that they were able to mediate neuroprotection by decreasing RNS, and in one particular embodiment, ONOO⁻. First, TEM analysis shows the incorporation of CeO₂ NPs by cortical neurons. TEM showed the association of CeO₂ NPs with membranes, both mitochondrial and plasma. These locations align with the primary sources of reactive nitrogen species in neurons. Sites of ONOO⁻ formation also include the mitochondrial membrane, due to the mitochondrial respiratory complexes, and plasma membrane NADPH oxidases.

The biochemistry of ONOO⁻ is vastly complicated due to the multiple reactions possible in the presence and absence of CO₂, H⁺ and metals during its decomposition (54, 55). Given its redox active nature, the interaction of CeO₂ NPs and ONOO⁻ was studied in vitro to improve the understanding of its biological capabilities. In vitro data using 302 nm absorbance and APF fluorescence assays were used to demonstrate that these CeO₂ NPs can speed the decomposition of ONOO⁻. This is decay held up even at higher pHs which may come into play when considering molecules that depend on tyrosine for their function. The pKa of the nitro-tyrosine (7.4) is considerably lower than tyrosine (10.07) (56). The nitration of the phenolic ring can inactivate enzymes and/or receptors that rely on phosphorylation of tyrosine for signaling. This newly identified catalytic property of CeO₂ NPs strengthens the evidence for the anti-oxidant properties (19, 20, 25).

The biological significance of CeO₂ NPs interaction with ONOO⁻ was then demonstrated. Oxidative and nitrosative stress occurs due to an imbalance of antioxidants and antioxidant enzymes to oxidants. Neurons have a high energy demand and contain several hundred mitochondria per cell and therefore have increased exposure to ROS and RNS (13). Though it cannot be ruled out that CeO₂ NPs are acting in addition as SOD mimetics, mitochondria are a primary site of the intercellular formation of ONOO⁻ (45) making neuronal cultures and by extension, neurodegenerative diseases an optimal prototype for exploring the biomedical applications of CeO₂ NPs.

Over-activation of the glutamate receptors has been linked to a number of disease conditions including neurodegenerative diseases such as Huntington's diseases (HD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD) (1). The excitatory amino acid glutamate has key roles in development of neurons and neurodegeneration through the activation of NMDA receptors which leads to increased oxidative and nitrosative stress (57). It has been discovered herein that treatments of cortical neurons with CeO2 NPs were able to protect from a variety of stressors, all of which increase RNS. These included treatments with 3-NP, glutamate, NMDA and Aβ peptide (25-35). The common molecular link between these conditions is an increase in production of ONOO⁻. In the case of 3-NP, a complex II inhibitor, depolarization of the mitochondrial membrane occurs followed by the rapid decrease of ATP, leads to an increase of NO· via the opening of the NMDA receptors (30). The NO· and increased O2^(·−) from the mitochondria lead to rising ONOO⁻ levels. Likewise, excess glutamate and NMDA can lead to NMDA receptor activation and with a subsequent increase in free radical production leading to increased ONOO⁻. Increased levels of ONOO⁻ levels then affect all biological molecules eventually causing neuronal dysfunction or death. Similarly, application of synthetic Aβ can modulate NMDA receptors (9). Aβ triggered neuronal dysfunction can also increase ONOO⁻. Aβ half-life in the central nervous system is normally 2 h but in AD, the half-life is increased due to altered clearance, therefore allowing increased chance of oligomerization. It has been found that CeO₂ NPs prevented the aggregation of the Aβ (1-40) peptide even in the presence of the metal chelator DPTA. This is important since many current therapeutic strategies use metal chelators to alter the progression of AD symptoms (58). Not only can CeO₂ NPs reduce the fibril formation in vitro but also the cell death caused Aβ (25-35) nitrosative stress. The findings provided herein are of broad significance in the search for an ONOO⁻ scavenger to inhibit the progression of neurodegenerative disorders, such AD, in which nitrosative stress plays a key role.

The results provided herein show that CeO₂ NPs protected cortical neurons from multiple nitrosative neuronal stressors. The intercellular location of the CeO₂ NPs likely enhances the scavenging of ONOO⁻. To further understand the mechanism of neuronal protection seen by CeO₂ NPs, ONOO⁻ and its ability to promote the nitration of tyrosine residues was considered. Specific nitrated proteins, such as, for example, Tau and the neurofilament light subunit (NF-L) have been heavily reported in literature to be linked to AD (59, 60). Modification of key proteins may result in detrimental change in function of the proteins. Tyrosine nitration modification of proteins has become an important marker for inflammation and has been detected in a number of diseases and pathological conditions (4). Disproportionate amounts of NO· can complete with oxygen causing the interruption of electrons from the respiratory chain which results in increased formation of O₂ ^(·−) (4) and thus increased ONOO⁻ leading to the post-translational modification of proteins. Increased levels of nitrated proteins have been reported in AD brains as well as cerebrospinal fluid in patients with AD (61). Reduction of nitrosative injury by CeO₂ NPs will lead to better therapeutic success of AD and reduction of neurodegeneration.

The results obtained in this study were the first to demonstrate that CeO₂ NPs can alter the decomposition of ONOO⁻, a newly identified and catalytic activity for CeO₂ NPs. CeO₂ NPs ability to readily react with ONOO⁻ has wide ranging implications for neurodegenerative disorders and aging. Once formed in the brain, ONOO⁻ can exert its toxic effects in many ways. Nitrotyrosine immunoreactivity has been implicated in the early stages of many diseases, including AD, PD, HD, multiple sclerosis (MS), and ALS (62-65). Widespread ONOO⁻ damage in AD has been demonstrated in many studies (7, 66). The ability of CeO₂ NPs to protect from these putative causative agents in AD, both cell death from Aβ peptide stress and 3-NT modifications by ONOO⁻ provides compelling rationale for further study into the molecular basis of this protection in diseases for which RNS may play a key role.

Moreover, nitrosative stress can activate kinases (74, 75). Specifically peroxynitrite can activate p38 MAP kinase and CdkS (76). Neurotoxic signals including Aβ and excess glutamate or NMDA causes an impaired Ca²⁺ homeostasis, which can activate downstream mediators including NOS and calpain (82). ROS/RNS can directly activate CdkS. Aberrant CdkS activation in neurodegeneration can occur by two mechanisms. First, nitrosative stress can directly activate Cdk5 by increasing its phosphorylation. Second, Ca²⁺-dependent calpain cleavage of the Cdk5 activator p35 to p25 increases its stability. Consequently, CdkS/p25 is constitutively activated. (77, 78, 79, 80). The blockage of mitochondrial fragmentation by nanoceria in response to Aβ was associated with a reduction in DRP1 5616 hyperphosphorylation (FIG. 8 b). Although it is unlikely that nitrosative stress mediates mitochondrial fragmentation and neuronal cell death only by phosphorylating a single protein target, such as DRP1, the present data describes one possible mode of action how nanoceria may specifically attenuate the downstream effects of RNS/ROS.

Most therapeutic treatments of AD have targeted reducing or clearance of Aβ with disappointing results however, therapeutic strategies aimed at reducing mitochondrial damage, especially through mitochondrial antioxidants (81) show promise. Considering nanoceria's proximity to mitochondria they may be uniquely situated to protect neurons in AD from nitrosative stress and mitochondrial dysfunction by lowering DRP1 5616 phosphorylation and thereby maintaining bioenergetic function and neuronal viability.

Nanoceria have been shown to decrease RNS/ROS-induced damage by many stress stimuli and in several cellular and animal models (20). No toxicity or adverse effects to nanoceria in the eyes of rats was found, where it prevents vision loss due to increased ROS from excess light exposure (19). Nanoceria also mitigate ischemic brain injury where nanoceria markedly decreased the levels of 3-nitrotyrosine (3-NT) (82) In addition, nanoceria accumulated on mitochondria, consistent with the provided results. The small size of nanoceria allowed passage into the neurons, but delivery routes into all cell types and tissues must still be tested. These are not trivial issues, yet considering the results that nanoceria protected cortical neurons from multiple nitrosative-associated stressors, they represent a potential exciting alternative strategy compared to traditional antioxidants. The present studies represent an important step forward to test the potential neuroprotective effects of nanoceria in in vivo animal models of AD.

MATERIALS AND METHODS FOR EXAMPLES 1-10 Reagents

EBSS (Earle's Balanced Salt Solution), Hank's buffer, Glutamax, B27, LipoFectamine2000®, and penicillin-streptomycin were purchased from Invitrogen (Carlsbad, Calif.). Neurobasal medium, Dulbecco's Modified Eagle's Medium (DMEM) was purchased from Hyclone (Logan, Utah). Poly-L-lysine, HEPES, glutamine, formaldehyde, N-acetyl-L-cysteine (NAC), anti-MAP2 antibodies (clone HM-2), anti-3-nitrotyrosine (3-NT), N-methyl-D-aspartate (NMDA), Ponceau S reagent, Durcupan ACM, 3-nitropropionic acid (3-NP), all Aβ peptides and all the chemicals for CeO₂ NPs synthesis were obtained from Sigma-Aldrich (St. Louis, Mo.). Hoechst 33342, AlexaFlour488, AlexaFluor594, pluronic acid, 3′-(p-aminophenyl) fluorescein (APF) (for cell culture), anti-β-actin antibody and PVDF membrane were purchased from Molecular Probes (Invitrogen). The DsRed2-Mito vector was obtained from Clontech (Mountain View, Calif.). Vector Shield was purchased from Vector Laboratories, Inc., (Burlingame, Calif.). T-Per extraction reagent was purchased from Pierce Biotechnology, Inc., (Rockford, Ill.). Nitrocellulose (Hybond) for dot blots and anti-mouse and anti-rabbit HRP-conjugated secondary antibodies came from ECL/GE Healthcare (Piscataway, N.J.). Peroxynitrite (ONOO⁻) and 2-[6-(4-aminophenoxy)-3-oxo-3H-xanthen-9-yl]-benzoic acid (APF) (for in vitro experiments) were purchased from Cayman Chemicals (Ann Arbor, Mich.). All reagents for transmission electron microscopy (TEM) were purchased from Ted Pella (Redding, Calif.). SiO₂ nanoparticles were purchased from Corpuscular Inc. (Cold Spring, N.Y.). In addition the following antibodies were used: monoclonal mouse-anti-DRP1 antibodies (clone 8/DLP1, BD Bioscience), rabbit polyclonal anti-p-DRP1 5616 antibodies (Cell Signaling), rabbit polyclonal 3-nitrotyrosine (Sigma), rabbit β-actin antibody (Cell Signaling); sheep-anti-mouse IgG-HRP (GE Healthcare), donkey-anti-rabbit IgG-HRP (GE Healthcare), goat-anti-mouse AlexaFluor488 (Invitrogen), goat-anti-rabbit AlexaFluor594 (Invitrogen).

Primary Neuronal Cultures

Purified or mixed cortical cultures were prepared from E18 rat embryos. Cells (400,000 cells/ml cell density) were plated in D10C medium (DMEM, 10% bovine calf serum, 2 mM glutamine, 25 mM HEPES, 10% F-12, and 0.25% penicillin-streptomycin) on poly-L-lysine (1 mg/ml) coated dishes. For pure cultures, the medium was replaced after 4 h with neurobasal medium supplemented with 2% B27, 2 mM Glutamax, and 1% penicillin-streptomycin. For live-cell imaging, phenol red-free neurobasal growth medium was used. Cultures were maintained at 37° C. in a humidified 5% CO₂ atmosphere and fed every 3-4 days as previously described (5, 30).

Scoring for Cell Death

Cultures were either transfected with DsRed2-Mito on day 5 using LipoFectamine2000® or immunostained for microtubule-associated protein 2 (MAP2) for visualization of processes. Experiments were performed after 11-14 days in vitro (DIV) with 3-NP, glutamate or NMDA. SNOC treated cultures were performed after 8 DIV. Neurons were pretreated with CeO₂ NPs for various time points, 3 h, 12 h, 24 h or 72 h. For cultures treated with 3-NP (diluted in EBSS and pH adjusted to 7.4 with NaOH), 3-NP was diluted in individual culture's conditioned medium before exchange and cultures left for 8 h. Brief exposure to NMDA was carried as follows. Culture medium was removed and saved and cultures washed with pre-warmed treatment buffer (1.8 mM CaCl₂, 5 M glycine in EBSS). Cells were exposed to NMDA (150 μM or 200 μM) for 20 min, washed with treatment buffer, conditioned media returned and then left for 12 h. Alternately, cells were treated with glutamate at various concentrations; 50 μM (13 h), 100 μM (4-6 h) or 150 μM (4-6 h). For Aβ (25-25) treated cultures, Aβ (25-35) or reverse (35-25) was left to oligomerize for 24 h at 25° C. before adding to cultures at 10 μM for 6 h. Cells were fixed in 3.7% formaldehyde and 5% sucrose in PBS for 20 min at 37° C. (to preserve mitochondrial morphology) or 4% paraformaldehyde for immunostaining. Cover slips were mounted with Vector Shield and sealed. Analyses were performed on triplicate coverslips of at least three independent experiments. Cells with fragmented mitochondria and condensed chromatin by Hoechst 33342 staining were scored as dead neurons. To evaluate mitochondrial fragmentation and cell death of a large number of neurons, manual scoring was carried out of neurons grown on glass coverslips using conventional fluorescence microscopy.

Mitochondrial Fragmentation and Neuronal Cell Death

Neurons were grown on poly-Lysine coated glass cover slips as described before and transfected with DsRed2-Mito after 5 days in vitro (DIV) using Lipofectamine2000®. Where indicated, neurons were pretreated with nanoceria for 3 h. 3-NP was prepared as previously described (30). The Aβ peptides were preaggregated as described before (5). Cell death was induced with 3-NP (10 mM, 8 h), glutamate (150 μM, 6 h), NMDA (150 μM, 12 h) Aβ (10 μM, 6 h) at 11-14 DIV or with SNOC (100 μM, 3 h) at 8 DIV. After various time periods neurons were fixed using 3.7% formaldehyde and 5% sucrose in PBS for 20 min at 37° C. Nuclei were labeled with Hoechst 33342 (1 μg/ml). Quantification of mitochondrial fragmentation and neuronal cell death was performed as described (30). Fluorescence microscopy and image acquisition of mitochondrial morphology was performed as previously described (98).

Immunocytochemistry

For immunocytochemistry, cortical cultures grown on glass coverslips were fixed in 4% formaldehyde in PBS buffer (pH 7.0; 20 min; 42° C.) and then permeabilized with 0.1 or 4% Triton X-100 in PBS (pH 7.4; 5 min; room temperature (RT)). Nonspecific binding was blocked with 3% BSA, 3% FBS in PBS for 1 h at room temperature. Cells were then probed with 3-NT (1:500) (RT, 2 h), and/or an antibody specific for MAP 2 protein (1:200) (RT, 2 h), a neuronal marker followed by a conjugated fluorescent secondary antibodies AlexaFluor594 or AlexaFluor488 (respectively) at dilutions of 1:500 (RT, 2 h). Chromatin was stained by incubating fixed samples with Hoechst 33342 (1 μg/ml) at RT for 20 min. For 3-NT, immuno-staining conditions were first optimized along with a blocking control, using 10 mM nitrotyrosine, to confirm specificity of 3-NT signal (31).

To visualize 3-NT using AlexaFluor594, the excitation filter was S555/28× (Chroma) and the emission filter was S617/73m (Chroma), to visualize neurons using AlexaFluor488, the excitation filter was S490/20× and the emission filter was S528/38m (Chroma) and to visualize Hoechst 33342 the excitation filter was S403/12× and emission filter S475/50m. Immuno-staining conditions for 3-NT were first optimized along with a blocking control, using 10 mM nitro-tyrosine, to confirm specificity of 3-NT signal. Fluorescence microscopy was performed as previously described (84). Quantification of fluorescence from 3-NT was as follows. Exposure time, brightness and contrast of randomly selected cortical neurons were held constant for all images within same experiment. Using MetaMorph 7.5, a region of interest was selected around each neuron using the MAP 2 label as a guide. This region was transferred to the 3-NT image channel. The fluorescence intensity for each neuron was measured using Show Region Statistics function. Area and intensity/fluorescence data was logged for each neuron. Twenty five to fifty neurons from each treatment were evaluated for a total of over 100 neurons per experiment. Three areas were selected randomly within each image and the average of their fluorescence intensity was considered as background. The background was subtracted within each image. 3-nitrotyrosine immuno-fluorescence quantification is expressed as fluorescence per μm².

Image Analysis

Fixed cell imaging was performed using an Axiovert Zeiss 100M inverted fluorescent microscope equipped with a plan Apochromat 63×1.4 NA oil objective, a DG-4/Lambda 10-2 combo Xe-arc illumination unit (shutter), and a Sensicam QE cooled CCD camera (PCO AG, Germany) controlled by MetaMorph 7.1 software (Molecular Devices). To visualize DsRed2-Mito and AlexaFluor594, the excitation filter was 5555/28× (Chroma) and the emission filter was S617/73m (Chroma). To visualize AlexaFluor488, the excitation filter was S490/20× (Chroma) and emission filter was S528/38m (Chroma). To visualize Hoechst staining for the nucleus, the emission filter was 475/50m (Chroma). Three dimensional images were acquired with the Multi Dimensional Acquisition module, 2×2 binning, 0.2-0.5 mm step size, and stacks of 10-21 z-planes.

Live Cell Imaging of Peroxynitrite

Neurons were seeded on MakTek petri dishes treated with poly-L lysine. For generation of ROS/RNS, the cultures were exposed to freshly prepared S-nitrosocysteine (SNOC) (50-200 μM), or aged SNOC (as control) for 2 h. To visualize ONOO⁻ , neurons (+/−CeO2 NPs) were loaded with imaging buffer (neural basal supplemented with 0.2% pluronic acid, 1.8 mM CaCl₂, 0.8 mM MgCl2) containing 2% APF also containing 1:10,000 Hoechst dye 33342 (1 μg/mL) for 30 min at 37° C. Dye was removed and replaced with conditioned phenol red-free NB medium. Fluorescence intensity was monitored in response to addition of SNOC. Z-stacks were acquired keeping exposure time, brightness and contrast constant for all images. Images were taken with 40× or 63× oil immersion objective lens and stored as tif files as visualized by excitation filter S490/20× (Chroma) and emission filter S528/38m (Chroma). From each sampled imaged, the number of APF positive cells were quantified by two independent methods: 1.) Manual scoring for presence of uncondensed nuclei or condensed nuclei with presence of dye; 2.) Using MetaMorph 7.5 software (Molecular Devices), equal backgrounds were subtracted from each z-stack image (as determined from control) then pixels from each z-stack series was summed. Cell soma and processes were selected and the number of pixels quantified per μm². This region was transferred to the APF image channel. The fluorescence intensity for each neuron was measured using Show Region Statistics function. Intensity/fluorescence data was logged for each neuron and data exported to Excel for further analysis.

Preparation of CeO₂ Nanoparticles

The ceria nanoparticles were synthesized by wet chemical process as previously described (32). In brief, for preparation of CeO₂ NPs with increased ratio of 3⁺/4⁺, Ce(NO₃)₃.6H₂O was dissolved in dH₂O and H₂O₂ was rapidly added with stirring at 300 rpm. The solution was then heated at 150° C. with continuous stifling to obtain a light yellow colored stable dispersion of cerium oxide nanoparticles. All CeO₂ NPs were sonicated (Branson, Danbury, Conn.) to prevent agglomeration for 45-60 min prior to use.

Western Blotting

To detect protein nitration, neurons were lysed using T-Per extraction reagent (Pierce) supplemented with Complete Protease Inhibitor Cocktail (Roche Applied Science, US). Protein concentrations were determined using the Bradford assay (Pierce Biotechnology, Inc., Rockford, Ill.). Proteins were separated by 4-20% SDS-PAGE gradient gels (Invitrogen) and transferred to PVDF membranes (0.2 μm, Bio-Rad). Nonspecific protein binding was blocked by incubating the membranes with TBS (50 mM Tris-Cl, pH 8.0, 150 mM NaCl), 0.02% Tween20, and 5% nonfat milk for 3 hours at room temperature. The membranes were then probed with primary rabbit polyclonal antibodies for 3-nitrotyrosine (Sigma) (1:500) overnight at 4° C. After four washes (5 min) of TBS (0.02% Tween20), membranes were incubated for two hours at room temperature with anti-rabbit horseradish peroxidase-conjugated secondary antibodies (GE Healthcare) (1:15,000) in blocking solution. After four washes (5 min) of TBS (0.02% Tween20), immunocomplexes were detected using the Super-Signal West-Dura chemiluminescence substrates (Pierce, Thermo Scientific, Rockford, Ill.). Restore Western Blot Stripping Buffer (Thermo-Scientific) was used to strip blots. Membranes were successively probed with anti-β-actin antibody (Cell Signaling, 1:1000).

To measure the levels of p-DRP1 5616, neurons were lysed in buffer containing 50 mM Tris-Cl, pH 7.0, 150 mM NaCl, 1 mM MgCl₂, 1 mM NaF, 1 mM NaVO₄, 1% NP40, 10% glycerol and complete Protease Inhibitor Cocktail Tablets (Roche Applied Science, US). Membranes were blocked with 5% nonfat milk in TBS (pH 8.0) with 0.05% Tween20 for 3 h at room temperature (RT) and were incubated with primary rabbit polyclonal antibodies for p-DRP1 5616 (Cell Signaling) (1:1000) overnight at 4° C. The membranes were then washed four times (5 min) with TBS (0.05% Tween) and incubated for 2 h at room temperature with anti-rabbit horseradish peroxidase-conjugated secondary antibodies (GE Healthcare) (1:15,000) in blocking solution. After 4 washes (5 min) of TBS (0.05% Tween), immunocomplexes were then detected using the Super-Signal West-Dura or Femto chemiluminescent substrates (Pierce, Thermoscientific, Rockfod, Ill.). For re-probing the membranes were stripped with Restore Western Blot Stripping Buffer (Thermo-Scientific) according to the manufacturer and incubated with mouse monoclonal antibodies for DRP1 (BD Biosciences, clone 8/DLP1) (1:1000) antibody or with polyclonal rabbit antibodies for β-actin (Cell Signaling) (1:1000).

3-Nitrotryosine Detection using Western Blot

Analysis of proteins for nitrotyrosine modification were isolated from mixed or pure neuronal cultures (8 DIV) after SNOC treatment +/−CeO₂ NPs using T-Per extraction reagent according to the manufacturer's recommendations, with the addition of the cOmplete Protease Inhibitor Cocktail Tablets (Roche Applied Science, US). Protein concentrations were determined using the Bradford assay (Pierce Biotechnology, Inc., Rockford, Ill.). To detect and for Western blot analysis, 25 μg of protein were fractionated by 4-20% SDS-PAGE gradient gels and transferred to PVDF membrane. Equal loading was evaluated by staining membranes with Ponceau S reagent and re-probing of blot using anti-β-actin antibody (1:1000).

Polymerization Dot Blot Assay

Aβ (1-40) oligomer (Sigma) was prepared with sterile H2O. The final Aβ concentration was 1 mg/ml. CeO₂ and SiO₂ NPs were added to 1 μg Aβ solutions to give final 100 nM, 100 μM and 1 mM. The samples were incubated for 7 d at 25 ° C. undisturbed. Samples were applied to nitrocellulose membrane in a Bio-Dot apparatus (Bio-Rad). The membrane was blocked with 10% nonfat milk in TBS-T at room temperature, washed with TBS-T, and probed with anti-oligomer A11 antibody solution (1:1,000) in 3% BSA-TBS-T overnight at 4° C. After washing, it was probed with anti-rabbit horseradish peroxidase-conjugated antibody (Pierce) solution (1:15,000) for 1 h at room temperature. For detection, West Dura substrate (Thermo Scientific, Rockford, Ill.) was used as per manufacture protocol and blots exposed to film (Hyperfilm; Amersham Pharmacia Corp.). The signals were quantified by densitometry using Image-J Software. The amount of oligomerization detected was normalized to the amount of background signal by NPs alone to yield a normalized estimate for the Aβ (1-40) oligomerization.

Monitoring Peroxynitrite In Vitro

ONOO⁻ (20 μM) was added to APF along with varying amounts CeO₂ NPs. Glutathione (Fisher, Fair Lawn, N.J.) and uric acid (Avocado, Research Chemicals, Ldt.) known scavengers of ONOO⁻, were used as positive controls. Fluorescence at 515 nm (ex. 490 nm) was measured using a Varian Cary Eclipse fluorescence spectrophotometer (Palo Alto, Calif.).

Monitoring Peroxynitrite Levels by UV-Visible Spectroscopy

UV-visible spectroscopy was used to measure decomposition of ONOO⁻ in the presence and absence of CeO₂ NPs. ONOO⁻ (20 μM) was added, while stifling, into a 1 mL quartz cuvette with a 1 cm path length. Each sample was analyzed for a total of 600 seconds with a cycle time of 0.5 seconds at a wavelength of 302 nm using buffer containing 100 mM sodium phosphate buffer (pH 9.5-8.0) and 1 μM diethylenetriaminepentaacetic acid (DPTA) with or without CeO₂ NPs. Spectrophotometric data was collected using a Hewlett-Packard diode array UV-visible 8453 spectrophotometer.

Transmission Electron Microscopy

Neurons were seeded on MakTek petri dishes coated with poly-L lysine. Cultures 11 DIV were treated with 100 nM CeO₂ NPs for 3 h, 12 h and 24 h. Neurons were fixed in 2% paraformaldehyde, 0.15 M sodium cacodylate, pH 7.4 and 2.5% glutaraldehyde for 5 min RT followed by 30 min on ice. Cultures were washed in ice cold 0.15 M sodium cacodylate and 3 μM calcium chloride 3×3 min on ice followed by post-fixation in 1% osmium tetroxide, 0.8% potassium ferricyanide, 3 μM calcium chloride in 0.15 M sodium cacodylate for 60 min on ice. After 3 washes in ice-cold ddH₂O (3 min), cultures were stained in 2% uranyl acetate for 30 min. Samples were dehydrated in ethanol series of ice-cold 20, 50, 70, 90 then 3 washes in 100% ethanol at RT for 3 min at final step. Samples were first infiltrated in 50% ethanol/50% Durcupan ACM (Fluka/Sigma) for 1 h at RT agitating, followed by 3 changes of 100% Durcupan for 3 h each at RT agitating. Resin was polymerized at 80° C. for 3-4 days under vacuum. Sectioning was performed using AO/Reichert Ultramicrotome.

The nanoparticle morphology was characterized using high-resolution transmission electron microscopy (HRTEM). The CeO₂ NPs were deposited on the carbon-coated copper grid for HRTEM analysis by the dip coating method. The HRTEM images of the as-prepared particles were obtained with a Philips (Tecnai Series) transmission electron microscope operating at 300 keV.

Electron Energy Loss Spectroscopy (EELS)

Sample preparation for EELS was an abbreviated protocol used for TEM preparation. Briefly, neurons were grown and treated as before but fixation was 2.5% glutaraldehyde in 0.1 M sodium cacodylate on ice for 30 min. Following 3×5 min rinses in ice-cold 0.1 M sodium cacodylate and 3 μM calcium chloride, cultures were postfixed in 0.5% osmium tetroxide with 3 μM calcium chloride in 0.1 M sodium cacodylate on ice for 20 min. Samples were dehydrated in ethanol series of ice-cold 20, 50, 70, 90% then 3 washes in 100% ethanol at RT for 1 min at final step. Samples were first infiltrated in 50% ethanol/50% Durcupan ACM for 30 min at RT agitating, followed by 3 changes of 100% Durcupan for at least 2 h at RT agitating. Resin was polymerized at 80° C. for 3-4 days under vacuum.

X-ray Photoelectron Spectroscopy (XPS)

CeO₂ NPs were treated with ONOO⁻ in 10 mM sodium phosphate buffer pH 7.4 and 50 μM DPTA. NPs were isolated by centrifugation at 20,000 RPM for 20 min, pellets dried and resuspended in same buffer. Samples were transferred onto silicon wafers and dried. The surface chemistry of the cerium oxide nanoparticles was studied using a Physical Electronics (5400 PHI ESCA) spectrometer with a monochromatic Al Kα X-ray source operated at 300 W and base pressure of 1×10⁻⁹ Torr. The binding energy of the Au (4f7/2) at 84.0±0.1 eV was used to calibrate the binding energy scale of the spectrometer.

Statistics

Results were collected from at least 3 replicates and are expressed as mean±S.D. Statistical analysis from two populations were compared using two-tailed, paired Student's t-test or between experiments using two-tailed non-paired Student's t-test.

Dosage

The dose administered to an animal, particularly a human, in accordance with the present invention should be sufficient to affect the desired response in the animal over a reasonable time frame. One skilled in the art will recognize that dosage will depend upon a variety of factors, including the strength of the particular compositions employed, the age, species, condition, and body weight of the animal. The size of the dose also will be determined by the route, timing and frequency of administration as well as the existence, nature, and extent of any adverse side effects that might accompany the administration of a particular composition and the desired physiological effect. It will be appreciated by one of ordinary skill in the art that various conditions or desired results, may require prolonged treatment involving multiple administrations.

Suitable doses and dosage regimens can be determined by conventional range-finding techniques known to those of ordinary skill in the art. Generally, treatment is initiated with smaller dosages, which are less than the optimum dose of the compound. Thereafter, the dosage is increased by small increments until the optimum effect under the circumstances is reached.

As used herein, by the term “effective amount,” “amount effective,” “therapeutically effective amount,” or the like, it is meant an amount effective at dosages and for periods of time necessary to achieve the desired result. The amount of the compound of the invention administered per dose or the total amount administered per day may be predetermined or it may be determined on an individual patient basis by taking into consideration numerous factors, including the nature and severity of the patient's condition, the condition being treated, the age, weight, and general health of the patient, the tolerance of the patient to the compound, the route of administration, pharmacological considerations such as the activity, efficacy, pharmacokinetics and toxicology profiles of the compound and any secondary agents being administered, and the like. Patients undergoing such treatment will typically be monitored on a routine basis to determine the effectiveness of therapy. Continuous monitoring by the physician will insure that the optimal amount of the compound of the invention will be administered at any given time, as well as facilitating the determination of the duration of treatment. This is of particular value when secondary agents are also being administered, as their selection, dosage, and duration of therapy may also require adjustment. In this way, the treatment regimen and dosing schedule can be adjusted over the course of therapy so that the lowest amount of compound that exhibits the desired effectiveness is administered and, further, that administration is continued only so long as is necessary to successfully achieve the optimum effect.

Pharmaceutical Compositions

As used herein, a “composition,” “pharmaceutical composition” “therapeutic composition” or “therapeutic agent” all include a composition comprising at least cerium oxide nanoparticles. Optionally, the “composition,” “pharmaceutical composition” “therapeutic composition” or “therapeutic agent” further comprises pharmaceutically acceptable diluents or carriers. In the case of an interfering molecule, for example, the interfering molecule may be combined with one or more pharmaceutically acceptable diluents, such as phosphate-buffered saline, for example. As used herein, a pharmaceutical composition particularly refers to a composition comprising at least a cerium oxide nanoparticle that is intended to be administered to a subject as described herein.

Various embodiments of the invention are foreseen to have valuable application as constituents of pharmaceutical preparations to treat various conditions generally defined as pathologies. Accordingly, embodiments of the invention also comprise pharmaceutical compositions comprising one or more compounds of this invention in association with a pharmaceutically acceptable carrier. Preferably these compositions are in unit dosage forms such as tablets, pills, capsules, powders, granules, sterile parenteral solutions or suspensions, metered aerosol or liquid sprays, drops, ampoules, auto-injector devices or suppositories; for oral, parenteral, intranasal, sublingual or rectal administration, or for administration by inhalation or insufflation. For preparing solid compositions such as tablets, the principal active ingredient is mixed with a pharmaceutical carrier, e.g. conventional tableting ingredients such as corn starch, lactose, sucrose, sorbitol, talc, stearic acid, magnesium stearate, dicalcium phosphate or gums, and other pharmaceutical diluents, e.g. water, to form a solid preformulation composition containing a homogeneous mixture of a compound of the present invention, or a pharmaceutically acceptable salt thereof. When referring to these preformulation compositions as homogeneous, it is meant that the active ingredient is dispersed evenly throughout the composition so that the composition may be readily subdivided into equally effective unit dosage forms such as tablets, pills and capsules. This solid preformulation composition is then subdivided into unit dosage forms of the type described above containing from 0.1 to about 500 mg of the active ingredient of the present invention. Typical unit dosage forms contain from 1 to 100 mg, for example 1, 2, 5, 10, 25, 50 or 100 mg, of the active ingredient. The tablets or pills of the novel composition can be coated or otherwise compounded to provide a dosage form affording the advantage of prolonged action. For example, the tablet or pill can comprise an inner dosage and an outer dosage component, the latter being in the form of an envelope over the former. The two components can be separated by an enteric layer which serves to resist disintegration in the stomach and permits the inner component to pass intact into the duodenum or to be delayed in release. A variety of materials can be used for such enteric layers or coatings, such materials including a number of polymeric acids and mixtures of polymeric acids with such materials as shellac, acetyl alcohol and cellulose acetate. The compositions may be contained in a vial, sponge, syringe, tube, or other suitable container.

As used herein, the terms “subject” and “patient” are used interchangeably. As used herein, the term “subject” refers to an animal, preferably a mammal such as a non-primate (e.g., cows, pigs, horses, cats, dogs, rats etc.) and a primate (e.g., monkey and human), and most preferably a human.

As used herein, the terms “treating” or “treatment” or “alleviation” refers to both therapeutic treatment and prophylactic or preventative measures, wherein the object is to prevent or slow down (lessen) the targeted pathologic condition or disorder.

As used herein, the term “administering” or “administration” includes but is not limited to oral or intravenous administration by liquid, capsule, tablet, or spray. Administration may be by injection, whether intramuscular, intravenous, intraperitoneal or by any parenteral route. Parenteral administration can be by bolus injection or by continuous infusion. Formulations for injection may be presented in unit dosage form, for example, in ampoules or in multi-dose containers with an added preservative. The compositions may take the form of suspensions, solutions or emulsions in oily or aqueous vehicles and may contain formulatory agents such as suspending, stabilizing and/or dispersing agents. Alternatively the compositions may be in powder form (e.g., lyophilized) for constitution with a suitable vehicle, for example sterile pyrogen-free water, before use. Compositions may be delivered to a subject by inhalation by any presently known suitable technique including a pressurized aerosol spray, where the dosage unit may be controlled using a valve to deliver a metered amount.

Administration by capsule and cartridges containing powder mix of the composition can be used in an inhaler or insufflator to deliver the particles to the subject. Still other routes of administration which may be used include buccal, urethral, vaginal, or rectal administration, topical administration in a cream, lotion, salve, emulsion, or other fluid may also be used.

It should be borne in mind that all patents, patent applications, patent publications, technical publications, scientific publications, and other references referenced herein are hereby incorporated by reference in this application in order to more fully describe the state of the art to which the present invention pertains.

Reference to particular buffers, media, reagents, cells, culture conditions and the like, or to some subclass of same, is not intended to be limiting, but should be read to include all such related materials that one of ordinary skill in the art would recognize as being of interest or value in the particular context in which that discussion is presented. For example, it is often possible to substitute one buffer system or culture medium for another, such that a different but known way is used to achieve the same goals as those to which the use of a suggested method, material or composition is directed.

It is important to an understanding of the present invention to note that all technical and scientific terms used herein, unless defined herein, are intended to have the same meaning as commonly understood by one of ordinary skill in the art. The techniques employed herein are also those that are known to one of ordinary skill in the art, unless stated otherwise. For purposes of more clearly facilitating an understanding the invention as disclosed and claimed herein, the following definitions are provided.

While a number of embodiments of the present invention have been shown and described herein in the present context, such embodiments are provided by way of example only, and not of limitation. Numerous variations, changes and substitutions will occur to those of skill in the art without materially departing from the invention herein. For example, the present invention need not be limited to best mode disclosed herein, since other applications can equally benefit from the teachings of the present invention. Also, in the claims, means-plus-function and step-plus-function clauses are intended to cover the structures and acts, respectively, described herein as performing the recited function and not only structural equivalents or act equivalents, but also equivalent structures or equivalent acts, respectively. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims, in accordance with relevant law as to their interpretation.

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1. A method of treating a subject with elevated levels of peroxynitrite, comprising: administering a therapeutically effective amount of cerium oxide nanoparticles to the subject, wherein the cerium oxide nanoparticles reduce the level of peroxynitrite in the subject.
 2. The method of claim 1, wherein the cerium oxide nanoparticles range between 1-5 nanometers in size.
 3. The method of claim 1, wherein the cerium oxide nanoparticles range between 5-10 nanometers in size.
 4. The method of claim 1, wherein said cerium oxide nanoparticles scavenge peroxynitrite.
 5. A method of treating a subject identified as at risk of developing a neurodegenerative disease, comprising: administering a therapeutically effective amount of cerium oxide nanoparticles (CeO2NPs) to the subject, wherein the cerium oxide nanoparticles scavenge reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the subject.
 6. The method of claim 5, wherein the RNS is peroxynitrite.
 7. The method of claim 5, wherein the patient at risk exhibits symptoms comprising at least one of the following: amyloid plaques in the brain or increased beta-amyloid deposits, neurofibrillary tangles (NFTs) in the brain, an atrophic brain region, atrophy of the hippocampus, increase in brain ventricle size, elevated levels of tau and/or amyloid beta proteins in cerebral spinal fluid, loss of function in the temporal lobe, cognitive deficiencies in memory, language, perceptual skills, attention, constructive abilities, orientation, problem solving, and/or functional abilities.
 8. The method of claim 5, wherein the patient at risk exhibits symptoms comprising at least two of the following: amyloid plaques in the brain or increased beta-amyloid deposits, neurofibrillary tangles (NFTs) in the brain, an atrophic brain region, atrophy of the hippocampus, increase in brain ventricle size, elevated levels of tau and/or amyloid beta proteins in cerebral spinal fluid, loss of function in the temporal lobe, cognitive deficiencies in memory, language, perceptual skills, attention, constructive abilities, orientation, problem solving, and/or functional abilities.
 9. The method of claim 5, wherein the patient at risk exhibits symptoms comprising at least one of the following: reduced dopaminergic activity in the basal ganglia, death of dopaminergic neurons in the substantia nigra pars compacta, motor symptoms comprising Parkinsonian gait, tremors, rigidity, slowness of movement, postural instability, non-motor symptoms comprising autonomic dysfunction, neuropsychiatric problems, sensory problems and/or sleep-related difficulties.
 10. The method of claim 5, wherein the patient at risk exhibits symptoms comprising at least two of the following: reduced dopaminergic activity in the basal ganglia, death of dopaminergic neurons in the substantia nigra pars compacta, motor symptoms comprising Parkinsonian gait, tremors, rigidity, slowness of movement, postural instability, non-motor symptoms comprising autonomic dysfunction, neuropsychiatric problems, sensory problems and/or sleep-related difficulties.
 11. (canceled)
 12. A method of scavenging reactive nitrogen species in a subject, comprising: administering a therapeutically effective amount of cerium oxide nanoparticles to the subject, wherein said cerium oxide nanoparticles associate with a membrane in the subject and accelerate decomposition of the reactive nitrogen species in the subject.
 13. The method of claim 12, wherein the reactive nitrogen species is peroxynitrite.
 14. The method of claim 12, wherein the membrane is a mitochondrial membrane and/or a plasma membrane.
 15. (canceled)
 16. The method of claim 1 wherein the cerium oxide nanoparticles comprise a higher 3+/4+ ratio.
 17. The method of claim 5 wherein the cerium oxide nanoparticles comprise a higher 3+/4+ ratio.
 18. (canceled)
 19. The method of claim 12 wherein the cerium oxide nanoparticles comprise a higher 3+/4+ ratio.
 20. The method of claim 15 wherein the cerium oxide nanoparticles comprise a higher 3+/4+ ratio. 